Concrete structures and construction methods

Abstract

Aspects of the invention relate to concrete structures having concrete columns. Cables can provides support as a flat beam in the horizontal slab above so that the columns can be used and largely spanned apart. The columns can be substantially aligned in a row or at least one column can be offset from the row of columns. Further, the concrete structure can include large cantilevered surfaces, such as balconies or walkways. Aspects of the invention further relate to a system for forming concrete columns using tunnel forms. In addition, embodiments of the invention can be used to form an offset column in a secondary pour. Aspects of the invention are particularly well suited for creating multi-level buildings of at least five stories.

1 . A method of forming a concrete column comprising the steps of: 
 attaching a column cage to a dowel set such that the column cage extends substantially vertically upward therefrom;    providing a pair of tunnel forms, each tunnel form having a first wall and a second wall extending substantially perpendicularly therefrom;    erecting the tunnel forms such that the second walls of the tunnel forms are substantially vertically oriented and opposingly spaced apart, wherein the column cage is disposed between the second walls;    positioning first blockouts substantially vertically in the space between the second walls such that the column cage is enclosed within a column space defined by the second walls of the tunnel forms and portions of the first blackouts;    positioning second blockouts substantially horizontally in the space between the second walls such that a substantially horizontal plane is defined by the first walls of the tunnel forms and portions of the second blockouts, wherein the second blockouts do not extend over the column space, whereby the second blockouts provide continuity of the first walls of the tunnel forms in the space between the second walls of the tunnel forms; and    pouring concrete on the substantially horizontal plane and within the column space so as to substantially simultaneously form a substantially horizontal slab and a substantially vertical column.    
   
   
       2 . The method of  claim 1  further including the steps of: 
 allowing the concrete to sufficiently cure; and    removing the tunnels forms.    
   
   
       3 . The method of  claim 2  further including the step of supporting the underside of the horizontal slab with shoring.  
   
   
       4 . The method of  claim 1  further including the steps of: 
 prior to the pouring step, positioning a plurality of metal chairs on the substantially horizontal plane; and    laying at least two post-tensioning cables over at least some of the metal chairs such that the cable is supported by the metal chairs and such that the cable extends directly over the column space.    
   
   
       5 . The method of  claim 4  further including the steps of: 
 allowing the concrete to sufficiently cure; and    tensioning the at least two cables, whereby the cable provides support as a flat beam in the horizontal slab so that the columns can be used and largely spanned apart.    
   
   
       6 . The method of  claim 4  further including the step of laying reinforcements over at least some of the metal chairs.  
   
   
       7 . A method of forming a concrete column offset from a row of columns comprising the steps of: 
 providing a first substantially horizontal concrete slab;    providing a pair of tunnel forms, each tunnel form having a first wall and a second wall extending substantially perpendicularly therefrom;    erecting the tunnel forms such that the second walls of the tunnel forms are substantially vertically oriented and opposingly spaced apart and such that a substantially horizontal plane is defined by the first walls of the tunnel forms;    placing a first blockout on the first wall of one of the tunnel forms, whereby the first blockout is provided in the desired location of a secondary poured column;    providing substantially horizontal reinforcements on top of the substantially horizontal plane proximate the first blockout;    providing substantially vertical reinforcements on top of the substantially horizontal plane, wherein the substantially vertical reinforcements extend in a substantially linear path from at least one side of the first blockout;    pouring concrete on top of the substantially horizontal plane so as to form a substantially horizontal second slab;    allowing the concrete to sufficiently cure; and    removing the tunnel forms and the first blockout, wherein the second slab includes an opening where the first blockout was positioned.    
   
   
       8 . The method of  claim 7  further including the step of supporting the underside of the second slab with shoring.  
   
   
       9 . The method of  claim 7  further including the steps of: 
 attaching a column cage to a dowel set provided on the first slab such that the column cage extends substantially vertically upward therefrom and through the slab opening;    providing a plurality of vertical forms between the first and second slabs so as to enclose the column cage in a column space therebetween, wherein the column space is directly beneath and substantially corresponds to the slab opening;    providing at least two opposing substantially vertical forms on top of the second slab, wherein the substantially vertical reinforcements extending from the second slab are disposed in the beam space between the forms;    pouring concrete into the column space and the beam space so as to substantially simultaneously form a concrete column, an upturn beam, and a portion of the second slab, wherein the column extends between and engages the first slab and the second slab, whereby the upturn beam structurally ties the concrete column to the second slab.    
   
   
       10 . A mid to high rise concrete structure comprising: 
 a first substantially horizontal concrete slab, the first slab having a plurality of concrete curbs extending substantially vertically upward therefrom;    a second substantially horizontal concrete slab, wherein the second slab is located above the first slab;    a plurality of substantially vertical concrete columns, each column extending between and engaging the second slab and one of the concrete curbs, wherein the columns are substantially aligned in a row; and    at least two post-tensioned cables extending through the second slab so as to extend over each of the columns, whereby the cables provide support as a flat beam between the concrete columns.    
   
   
       11 . The structure of  claim 10  wherein the columns and the second slab are monolithic.  
   
   
       12 . The structure of  claim 10  further including anchors near each end of the second slab, wherein the anchors hold the at least two cables in tension.  
   
   
       13 . The structure of  claim 10  wherein the column width is at least about 8 inches in any direction.  
   
   
       14 . The structure of  claim 10  wherein the columns are substantially rectangular.  
   
   
       15 . The structure of  claim 10  wherein the cables span in substantially one direction, whereby the cables provide substantially unidirectional support as a flat beam to the second slab such that the second slab is one way reinforced.  
   
   
       16 . The structure of  claim 10  further including reinforcements in the second slab, wherein at least some of the reinforcements extend over the concrete column.  
   
   
       17 . The structure of  claim 16  wherein the reinforcements extend through the second slab in substantially the same direction as the cables, wherein at least some of the reinforcements extend over the columns.  
   
   
       18 . The structure of  claim 16  wherein the reinforcements extend through the second slab so as to be substantially transverse to the cables, wherein at least some of the reinforcements extend over the columns.  
   
   
       19 . The structure of  claim 10  wherein the cables extend through the second slab in a substantially undulating manner.  
   
   
       20 . A mid to high rise concrete structure with a column offset from a row of columns comprising: 
 a first substantially horizontal concrete slab, the first slab having a plurality of concrete curbs extending substantially vertically upward therefrom;    a second substantially horizontal concrete slab, wherein the second slab is located above the first slab;    a plurality of substantially vertical concrete columns, each column extending between and engaging the second slab and one of the concrete curbs, wherein the columns are substantially aligned in a row;    a column offset from the row of concrete columns, wherein the offset column extends between and engages the first and second slabs;    an upturn beam extending substantially vertically upward from the second slab, the upturn beam being structurally connected to the second slab, wherein the upturn beam, the offset column and a portion of the second slab are monolithic, whereby punching shear due to the cold joint around the offset column is substantially prevented;    at least two post-tensioned cables extending through the second slab so that the cables extend over each of the columns and substantially proximate to the offset column, whereby the cables act as a flat beam between the concrete columns.    
   
   
       21 . The structure of  claim 20  wherein the upturn beam is structurally connected to the second slab by a plurality of stirrups extending up from the second slab and into the upturn beam.  
   
   
       22 . The structure of  claim 20  further including at least one substantially vertical concrete support extending between and engaging the second slab and a curb, wherein the vertical support, a portion of the second slab and the upturn beam are monolithic, wherein the upturn beam spans between the vertical support and the offset column.  
   
   
       23 . The structure of  claim 22  wherein the vertical support is substantially parallel to the row of columns.  
   
   
       24 . The structure of  claim 22  wherein the upturn beam is substantially perpendicular to at least one of the vertical support and the row of columns.  
   
   
       25 . The structure of  claim 20  further including anchors near each end of the second slab, wherein the anchors hold the at least two cables in tension.  
   
   
       26 . The structure of  claim 20  wherein the cables span in substantially one direction, whereby the cables provide substantially unidirectional support to the second slab, whereby the second slab in one way reinforced.  
   
   
       27 . The structure of  claim 20  further including reinforcements in the second slab, wherein at least some of the reinforcements extend over the concrete column.  
   
   
       28 . The structure of  claim 27  wherein the reinforcements extend through the second slab in substantially the same direction as the cables.  
   
   
       29 . The structure of  claim 27  wherein the reinforcements extend through the second slab so as to be substantially transverse to the cables.  
   
   
       30 . The structure of  claim 20  wherein the cables extend through the second slab in a substantially undulating manner.  
   
   
       31 . A concrete structure with a cantilevered slab comprising: 
 a first substantially horizontal concrete slab, the first slab having a plurality of concrete curbs extending substantially vertically upward therefrom;    a second substantially horizontal concrete slab, wherein the second slab is located above the first slab;    a plurality of substantially vertical concrete columns, each column extending between and engaging the second slab and one of the concrete curbs, the columns being substantially aligned in a row, wherein the row of columns includes a first end column and a second end column, wherein a portion of the second slab extends cantilevered beyond at least one of the end columns;    at least two post-tensioned cables extending through the second slab including the cantilevered portion so as to extend over each of the columns, whereby the cables act as a flat beam over the row of columns to support the cantilevered slab.    
   
   
       32 . The structure of  claim 31  wherein the columns and the second slab are monolithic.  
   
   
       33 . The structure of  claim 31  wherein the length of the cantilevered portion of the second slab is at least about 8 feet.  
   
   
       34 . The structure of  claim 31  wherein the cables extend through the second slab in a substantially undulating manner.